IMPLICATION OF FORMATION MECHANISMS OF HC sub(5) N IN TMC-1 AS STUDIED BY super(13) C ISOTOPIC FRACTIONATION

We observed the J= 9 - 8 and 16 - 15 rotational transitions of the normal species and five super(13) C isotopologues of HC sub(5) N to study its formation mechanisms toward the cyanopolyyne peak in Taurus Molecular Cloud-1, with the 45-m radio telescope of the Nobeyama Radio Observatory. We detected the five super(13) C isotopologues with high signal-to-noise ratios between 12 and 20, as well as the normal species. The abundance ratios of the five super(13) C isotopologues of HC sub(5) N are found to be 1.00:0.97:1.03:1.05:1.16 (+ or -0.19) (1[sigma]) for [H super(13) CCCCCN]:[HC super(13) CCCCN]:[HCC super(13) CCCN]:[HCCC super(13) CCN]:[HCCCC super(13) CN]. We do not find any significant differences among the five super(13) C isotopologues. The averaged [HC sub(5) N]/[ super(13) C isotopologues] abundance ratio is determined to be 94 + or - 6 (1[sigma]), which is slightly higher than the local interstellar elemental super(12) C/ super(13) C ratio of 60-70. Possible formation pathways are discussed on the basis of these results.